Technical Field
The present disclosure relates to an organic light-emitting display device, and more specifically to an organic display device capable of reducing light leakage in a horizontal direction and improving color viewing angle characteristics in the horizontal direction.
Description of the Related Art
An organic light-emitting display device is a self-luminance display device and thus does not require an additional light source, such as a backlight for liquid crystal display (LCD) devices. Therefore, organic light-emitting display devices can be made lighter and thinner. Further, an organic light-emitting display device has advantages in that it is driven with low voltage to consume less power, and represents vivid colors, has a short response time, a wide viewing angle and a good contrast ratio (CR). For these reasons, an organic light-emitting display device is currently under development as the next generation display device.
An organic light-emitting display device displays images by using light emitted from an organic light-emitting element connected to a thin-film transistor (TFT) in each of the pixels or sub-pixels. The organic light-emitting element includes an emission layer made of an organic material formed between an anode and a cathode and emits light by applying an electric field across them, such that it can be driven with low voltage to consume less power, is light, and is applicable to a flexible upper substrate.
Organic light-emitting display devices may be divided into a top-emission organic light-emitting display device and a bottom-emission organic light-emitting display device, depending on a direction in which light exits. A bottom-emission organic light-emitting display device has high stability and high processing freedom degree, but has a limited aperture ratio and thus is difficult to be applied to high resolution products. For these reasons, a top-emission organic light-emitting display device is being recently studied.
For organic light-emitting display devices, a light source for three colors including red (R), green (G) and blue (B) is used to represent the full white color scheme.
Among methods for implementing a light source for three colors, there is a method in which red, green and blue organic light-emitting layers are formed in sub-pixels, respectively, such that each of the sub-pixels emits light independently. There is another method in which a plurality of emission layers are stacked one on another to form white organic light-emitting elements in a multi-stack configuration, and red, green or blue color filters are disposed thereon to emit light of a color via the color filter.
Such an existing organic light-emitting display device using white organic light-emitting elements in multi-stack and color filters may include a first substrate on which thin-film transistors and organic light-emitting elements are formed, and an opposing second substrate on which color filters are formed.
FIG. 1 is a plan view of an existing organic light-emitting display device having pixels arranged in vertical stripes.
Referring to FIG. 1, an existing organic light-emitting display device 10 having color filters may include a plurality of pixels 13 disposed on a substrate, each of the plurality of pixels 13 including a first sub-pixel 14, a second sub-pixel 15, a third sub-pixel 16 and a fourth sub-pixel 17.
In addition, referring to FIG. 1, the color filters disposed on a second substrate of the organic light-emitting display device 10 may include a red color filter R-CF, a green color filter G-CF, a blue color filter B-CF and a white color filter W-CF, which correspond to the first sub-pixel 14, the second sub-pixel 15, the third sub-pixel 16 and the fourth sub-pixel, respectively.
A black matrix (BM) 19 is formed between every two of the red color filter R-CF, the green color filter G-CF, the blue color filter B-CF and the white color filter W-CF on the second substrate of the organic light-emitting display device 10, so as to block light passing through one of the color filters from propagating to an adjacent color filter such that colors are not mixed in the adjacent pixel.
Typically, as can be seen from FIG. 1, in the existing organic light-emitting display device 10 including white organic light-emitting elements in multi-stack, color filters, and thin-film transistors, the organic light-emitting elements and corresponding color filters are arranged in vertical stripes.
Specifically, each of the first sub-pixel 14, the second sub-pixel 15, the third sub-pixel 16 and the fourth sub-pixel 17 in the pixel 13 are extended in a second direction Y that is a column direction of the organic light-emitting display device 10, rather than in a first direction X that is a row direction of the organic light-emitting display device 10. In addition, the first sub-pixel 14, the second sub-pixel 15, the third sub-pixel 16 and the fourth sub-pixel 17 are arranged sequentially such that they are adjacent to one another in the first direction X of the organic light-emitting display device 10.
FIG. 2 is a cross-sectional view taken along line II-II′, which shows an example of light leakage in a horizontal direction occurring in an existing organic light-emitting display device 10 having pixels arranged in vertical stripes.
That is, FIG. 2 is a cross-sectional view taken along line II-II′ illustrating light leakage in the horizontal direction occurring in an existing organic light-emitting display device 10 having pixels arranged in vertical stripes.
Referring to FIG. 2, a first substrate 11 may include a thin-film transistor 112 disposed on the first substrate 11, a first electrode 14a disposed on the thin-film transistor 112 in a first sub-pixel 14, a first electrode 15b formed in a second pixel 15, and a bank 18 disposed on the first electrodes 14a and 15b and between the first sub-pixel 14 and the second sub-pixel 15 to define the emission area of each of the sub-pixels. An emission layer formed by stacking a plurality of organic layers may be disposed on the first electrodes 14a and 15b and the bank 18.
In addition, referring to FIG. 2, a second substrate 12 facing the first substrate 11 may include a red color filter R-CF disposed in the first sub-pixel 14, a green color filter G-CF disposed in the second sub-pixel 15, and a black matrix (BM) 19 disposed between the red color filter R-CF and the green color filter G-CF.
The existing organic light-emitting display device 10 shown in FIG. 2 is fabricated by attaching the first substrate 11 including the first electrodes 14a and 15b and the emission layer to the second substrate 12 including the red color filter (R-CF) and the green color filter (G-CF). In doing so, the first substrate 11 or the second substrate 12 may deviate from a designed location, such that a misalignment ‘A’ may occur between the bank 18 disposed on the first substrate 11 and the black matrix 19 disposed on the second substrate 12.
If the misalignment ‘A’ occurs as shown in FIG. 2, light exiting through the first electrode 14a of the first sub-pixel 14 is not blocked by the black matrix 19. The light may exit through the green color filter G-CF formed in the second sub-pixel 15 adjacent to the first sub-pixel 14, as well as the red color filter R-CF, resulting in light leakage in the horizontal direction of the organic light-emitting device 10. As such, a color of a pixel may be represented in another pixel adjacent to the pixel, which is undesirable. As a result, color viewing angle characteristics of the organic light-emitting display device 10 may be deteriorated.
In addition, light leakage in the horizontal direction due to the misalignment ‘A’ in the organic light-emitting display device 10 may be affected also by a variation in a cell gap (i.e., the distance between the first and second substrates 11 and 12). This is also a problem to be improved.